1. Field of the Invention
The present invention relates to milling of wheat or the like and, more particularly, to a flour milling method and a system therefor in which the wheat polishing is carried out as a preparatory step.
2. Description of the Prior Art
Milling is a process wherein wheat or the like is ground and pulverized to collect endosperm portions in a powder condition such that bran portions containing much ash contents (unwanted components) are not mixed with the endosperm portions while the endosperm portions (weight conversion percentage: approximately 84%), the bran portions (the same: 13.5%) having a plurality of layers, such as a pericarp layer, a testa layer and a layer of exosperm, on the outside of the endosperm portions, and embryos (the same: 2.5%) are separated from each other. However, it is extremely difficult to completely separate the endosperm portions and the bran portions from each other. A collecting rate (yield) of products relatively low in mixing of the bran portions is normally in the order of 75%.
Whereas the milling method (milling of raw wheat) as described above in which wheat kernels as raw material (hereinafter referred to as "raw wheat") are directly ground and pulverized, a milling method (milling of polished wheat) in which bran portions of the raw wheat are peeled off or separated to expose endosperm portions and, subsequently, the wheat is ground and pulverized is well known from, for example, Japanese Patent Application Kokai No. Sho 62(1987)-87250 filed by the same applicant.
Polishing prior to the milling of wheat contributes to the reduction in the necessary number of roll machines or the like and also contributes to the improvement in a milling efficiency. However, this method has the following problems. Specifically, the wheat polishing is usually executed such that a grinding polishing roll made of emery is mounted within a bran-removing polishing cylinder having a perforated wall to define a polishing chamber, and bran portions of the wheat kernels other than longitudinal grooves (creases) thereof are shaved off in the polishing chamber. However, there is a disadvantage that the separated bran portions enter into the longitudinal creases so that a milling characteristic is deteriorated.